(Adapted from applicant's abstract): This project proposes to compare the neurochemical and morphologic features of pediatric HIV cases with those of the late-onset dementias. Because the neurologic deficits in HIV infection occur in the context of a developing brain, the neurochemistry and morphology of HIV-infected brains will be compared with those of the brains of age-matched non-infected children. A systematic study of the staining patterns of antibodies in HIV-infected brains will be undertaken, comparing the results with an extensive series of studies of adult dementias which have been previously performed by the investigators. Antibodies that reveal consistent abnormalities in pediatric cases will be used on HIV-fetal brain tissue to attempt to determine at what stage in development neuronal systems begin to deteriorate, and on fetal brain tissue explants in culture, with and without HIV infection.